U.S. patent application number 10/433995 was filed with the patent office on 2004-02-26 for mixing device comprising a swirl chamber for mixing liquid.
Invention is credited to Den Hartog, Arie Pieter, Den hartog-Snoeij, Maria, Van Vliet, Willem.
Application Number | 20040037759 10/433995 |
Document ID | / |
Family ID | 8173437 |
Filed Date | 2004-02-26 |
United States Patent
Application |
20040037759 |
Kind Code |
A1 |
Van Vliet, Willem ; et
al. |
February 26, 2004 |
Mixing device comprising a swirl chamber for mixing liquid
Abstract
The invention relates to a mixing device (5) for mixing fluids
in a multiple bed downflow reactor comprising: (i) a substantially
horizontal collection tray (6); (ii) a swirl chamber (7) for mixing
liquid arranged below the collection tray (6), having an upper end
part that is in direct fluid communication with the upper surface
(9) of the collection tray (6) and an outlet opening (10) at its
lower end, wherein the swirl chamber (7) has a length that is at
least 0.35 times its inner diameter; and (iii) a substantially
horizontal distribution tray (13) located below the swirl chamber
(7), which distribution tray (13) is provided with a plurality of
openings or downcomers (14) for downward flow of liquid and gas.
The invention further relates to a multiple bed downflow reactor
comprising such a mixing device and to the use of such a reactor in
hydrocarbon processing.
Inventors: |
Van Vliet, Willem; (The
Hague, NL) ; Den Hartog, Arie Pieter; (Leidschendam,
NL) ; Den hartog-Snoeij, Maria; (Leidschendam,
NL) |
Correspondence
Address: |
Richard F Lemuth
Shell Oil Company
Intellectual Property
PO Box 2463
Houston
TX
77252-2463
US
|
Family ID: |
8173437 |
Appl. No.: |
10/433995 |
Filed: |
June 10, 2003 |
PCT Filed: |
December 11, 2001 |
PCT NO: |
PCT/EP01/14736 |
Current U.S.
Class: |
422/607 ;
422/211; 422/220; 422/224 |
Current CPC
Class: |
B01F 23/2322 20220101;
B01J 8/0453 20130101; C10G 49/002 20130101; B01J 8/0492 20130101;
B01J 8/0085 20130101; B01J 2208/00132 20130101; B01J 8/0496
20130101 |
Class at
Publication: |
422/195 ;
422/211; 422/191; 422/220; 422/224; 422/194 |
International
Class: |
B01J 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2000 |
EP |
00311008.7 |
Claims
1. A mixing device for mixing fluids in a multiple bed downflow
reactor comprising: (i) a substantially horizontal collection tray;
(ii) a swirl chamber for mixing liquid arranged below the
collection tray, having an upper end part that is in direct fluid
communication with the upper surface of the collection tray and an
outlet opening at its lower end, wherein the swirl chamber has a
length that is at least 0.35 times its inner diameter; and (iii) a
substantially horizontal distribution tray located below the swirl
chamber, which distribution tray is provided with a plurality of
openings or downcomers for downward flow of liquid and gas.
2. A mixing device according to claim 1, wherein the length of the
swirl chamber is at least 0.5 times its inner diameter, preferably
at least 0.65 times its inner diameter.
3. A mixing device according to claim 1 or 2, wherein the
collection tray is further provided with means for passage of gas,
preferably in the form of at least one downcomer extending through
the collection tray, the downcomer(s) being provided with a gas
inlet opening located above the collection tray and a gas outlet
opening located at the level of the lower surface of or below the
collection tray.
4. A mixing device according to any one of the preceding claims,
which further comprises means for distributing a quench fluid, the
means being located above the collection tray.
5. A mixing device according to any one of the preceding claims,
which further comprises a substantially horizontal pre-distribution
tray arranged between the swirl chamber and the distribution
tray.
6. A multiple bed downflow reactor comprising vertically spaced
apart reaction beds, preferably beds of catalyst particles, and,
between adjacent beds, a mixing device as defined in any one of the
preceding claims.
7. Use of a multiple bed downflow reactor as defined in claim 6 in
hydrocarbon processing.
Description
[0001] The present invention relates to a mixing device for mixing
fluids in a multiple bed downflow reactor, to a multiple bed
downflow reactor comprising such a device and to the use of such a
reactor in hydrocarbon processing.
[0002] A multiple-bed downflow reactor is a reactor in which gas
and liquid flow co-currently downward through a number of reaction
beds arranged one below the other. Such reactors are used in the
chemical and petroleum refining industries for effecting various
processes such as catalytic dewaxing, hydrotreating and
hydrocracking. In these processes a liquid phase is typically mixed
with a gas phase and the mixed fluids are passed over a particulate
catalyst maintained in the reaction beds. As the fluids pass
concurrently through a reaction bed, the distribution of liquid and
gas across the reaction bed will tend to become uneven with adverse
consequences with regard to the extent of reaction and also
temperature distribution. In order to achieve a uniform
distribution of liquid and gas and of temperature in the fluids
entering the next lower reaction bed, a fluid mixing device, of
which there are many different types, is usually placed between the
reaction beds. These devices provide for liquid-liquid, gas-gas,
and gas-liquid mixing and for homogenous distribution of the mixed
fluids over the next lower reaction bed.
[0003] Such fluid mixing devices are known in the art. Known fluid
mixing devices, for example from EP 716 881, WO 97/46303, and WO
99/28024, have the advantage that they have a relatively low
vertical length, thereby minimising the space and volume
requirements for the devices.
[0004] It has, however, been found that these known small-length
mixing devices have the disadvantage that fluid mixing is not
optimal when gas and/or liquid loads deviate importantly from their
normal values, i.e. at high turn-down ratios. Important deviations
from the normal values may for example occur after modification of
a reactor, modification of a process line-up of which the reactor
forms part, or use of an existing reactor for a different
purpose.
[0005] Thus, there is a need in the art for fluid mixing devices
that provide for a good fluid mixing performance over a wide range
of gas and liquid loads, i.e. at high turn-down ratios. An object
of the present invention is to find an optimum between the length
of the mixing device and the fluid mixing performance at high
turn-down ratios.
[0006] It has now been found that an excellent mixing performance
over a wide range of gas and liquid loads, typically from as low as
33% to as high as 200% of the normal loads, can be achieved by
using a mixing device wherein the liquid-liquid mixing is performed
in a swirl chamber having a certain ratio of length and
diameter.
[0007] Accordingly, the present invention relates to a mixing
device for mixing fluids in a multiple bed downflow reactor
comprising:
[0008] (i) a substantially horizontal collection tray;
[0009] (ii) a swirl chamber for mixing liquid arranged below the
collection tray, having an upper end part that is in direct fluid
communication with the upper surface of the collection tray and an
outlet opening at its lower end, wherein the swirl chamber has a
length that is at least 0.35 times its inner diameter; and
[0010] (iii) a substantially horizontal distribution tray located
below the swirl chamber, which distribution tray is provided with a
plurality of openings or downcomers for downward flow of liquid and
gas.
[0011] For optimal fluid mixing, especially at high turndown
ratios, it is preferred that the swirl chamber has a length that is
at least 0.50 times its inner diameter, more preferably at least
0.65 times its inner diameter. In order to limit the length of the
mixing device and therewith the volume occupied in the reactor, the
length will generally not be larger than 1.5 times its inner
diameter.
[0012] Reference herein to the length of the swirl chamber is to
the vertical distance between the lower point of its inlet or
inlets and its outlet opening. In the case of a polygonal swirl
chamber, reference herein to its inner diameter is to the largest
cross-sectional distance between opposite side walls through the
central axis of the chamber.
[0013] The mixing device according to the invention may comprise
more than one swirl chamber. Preferably it has one swirl chamber
located along the central longitudinal axis of the mixing
device.
[0014] The substantial horizontal collection tray of the mixing
device of the present invention may be curved or conical, provided
that the upper end part of the swirl chamber is in direct fluid
communication with the upper surface of the lowest point of the
collection tray. Reference herein to a substantial horizontal tray
is to a tray having its symmetry axis perpendicular to the
horizontal plane. Preferably, the collection tray is flat.
[0015] Preferably, the collection tray is further provided with
means for passage of gas, preferably in the form of at least one
downcomer extending through the collection tray, the downcomer(s)
being provided with a gas inlet opening located above the
collection tray and a gas outlet opening located at the level of
the lower surface of or below the collection tray. The downcomer(s)
is/are preferably provided with a fluid deflector plate located
above the gas inlet opening. The gas outlet opening may be axial or
radial. Preferably, the downcomer has a radial outlet opening in
combination with a curved plate that directs the gas to the radial
outlet opening in order to minimise pressure drop.
[0016] The mixing device may further comprise means for
distributing a quench fluid located above the collecting tray, in
order to achieve cooling of effluent between the reaction beds of a
multiple-bed downflow reactor. Means for distributing a quench
fluid are well known in the art and are described, for example, in
EP 427 733, U.S. Pat. No. 3,787,189 and U.S. Pat. No.
3,855,068.
[0017] The mixing device has a distribution tray below the outlet
opening of the swirl chamber for evenly distributing gas and liquid
before the fluids enter a lower reaction bed. Suitable distribution
trays are known in the art, for example from EP 716 881, EP 715
544, and U.S. Pat. No. 5,989,502. A preferred distribution tray is
the one disclosed in EP 716 881.
[0018] The mixing device of the present invention may further
comprise a substantially horizontal pre-distribution tray arranged
between the swirl chamber and the distribution tray. Such
pre-distribution trays are known in the art. The pre-distribution
tray may be round, square or rectangular in shape and has
preferably a diameter that is smaller than the diameter of the
distribution tray. Preferably, the pre-distribution tray is
provided with an overflow weir at its perimeter. The tray is
provided with a plurality of openings, preferably located near its
perimeter. The advantages of having a pre-distribution tray are
that it enables liquid to be spread more evenly over the
distribution tray and it helps to promote liquid-liquid
interactions and thus liquid equilibration.
[0019] The present invention further relates to a multiple bed
downflow reactor comprising vertically spaced apart reaction beds,
preferably beds of catalyst particles, and, between adjacent
reaction beds, a mixing device as hereinbefore defined.
[0020] Such a reactor has at least one inlet for gas and/or liquid,
at least one outlet for reactor effluent and at least two
consecutive reaction beds, typically beds of catalyst particles,
each bed resting upon a support tray. The construction of suitable
support trays is known in the art. For instance, commonly applied
support trays comprise one or more permeable plates such as sieve
plates supported by support beams, whereby the catalyst bed rests
upon the said permeable plates. Gaseous and liquid products formed
in the reactions occurring in the catalyst bed are passed through
the permeable plates to the subsequent catalyst bed or reactor
outlet. Such reactors are typically used in the hydroprocessing of
hydrocarbon oils.
[0021] In a further aspect, the invention relates to the use of a
multiple bed downflow reactor as hereinbefore defined in
hydrocarbon processing, preferably in catalytic dewaxing,
hydrotreating, hydrocracking, or hydrodesulphurisation.
[0022] The mixing device and the reactor according to the invention
will now be illustrated by way of example by means of schematic
FIGS. 1 and 2. Similar parts in different figures are referred to
with the same reference numerals.
[0023] FIG. 1 is a longitudinal section of part of a reactor
according to the invention showing an embodiment of the mixing
device according to the invention and the catalyst beds located
above and below the mixing device.
[0024] FIG. 2 shows a longitudinal section of the downcomer for gas
of the mixing device shown in FIG. 1, the section being through
line II-II in the plane perpendicular to the plane of the drawing
of FIG. 1.
[0025] In FIG. 1 is shown part of the side wall 1 and two adjacent
catalyst beds 2a and 2b of a multiple-bed reactor. The catalyst
beds 2a and 2b are supported on sieve plate 3, supported by support
beams (not shown). A mixing device 5 according to the invention is
positioned between catalyst beds 2a and 2b. The mixing device 5
comprises a flat, horizontal collection tray 6 and a swirl chamber
7 arranged below the collection tray 6. The swirl chamber 7 has an
open upper end 8 that is in direct fluid communication with the
upper surface 9 of collection tray 6, an outlet opening 10 at its
lower end, and means 11 for imposing a swirling action on the
liquid passing through it. The mixing device 5 comprises means for
passage of gas in the form of three downcomers for gas 12 (only one
downcomer shown) extending through the collection tray 6. A
distribution tray 13 provided with a plurality of downcomers 14 is
located below swirl chamber 7 and a pre-distribution tray 15
comprising an overflow weir 16 and a plurality of openings 17 is
located between swirl chamber 7 and distribution tray 15. The
mixing device further comprises a quench ring 18.
[0026] During normal operation of the mixing device shown in FIG.
1, effluent from catalyst bed 2a is cooled by quench fluid from
quench ring 18. The liquid effluent is collected on collection tray
6 and enters swirl chamber 7 through its open upper end 8. In the
swirling chamber 7, a swirling movement is imposed on the liquid by
swirling means 11. Suitable means for imposing a swirling action on
fluids are known in the art, for example a tangential inlet
opening, swirling vanes or baffles attached to the inner surface of
the side wall of the swirl chamber or the like. The combination of
a swirling action imposed on the liquid and the length of the
swirling chamber result in excellent liquid-liquid mixing over a
wide range of liquid and gas throughput. It is an advantage of the
mixing device according to the invention that the degree of
liquid-liquid mixing achieved in swirl chamber 7 is practically
independent of the gas load. The mixed liquid leaves the swirl
chamber 7 via outlet opening 10. Preferably, the swirling chamber 7
is provided with vanes (not shown) or the like near the outlet
opening 10 to stop the swirling movement of the liquid and thus
increasing turbulence and further improving liquid-liquid
mixing.
[0027] Effluent gas from catalyst bed 2a passes collection tray 6
via downcomers for gas 12. Part of the effluent gas may pass
collection tray 6 via swirl chamber 7. It will be appreciated that
it will inter alia depend on the gas and liquid loads and on the
size, shape and location of the inlet(s) of the swirl chamber and
the gas inlet opening(s) of the means for passage of gas, what part
of the effluent gas will pass through the means for gas passage and
what part through the swirl chamber.
[0028] Alternatively, the mixing device according to the invention
does not comprise separate means for passage for gas, in which case
all effluent gas will pass the collection tray via the swirl
chamber.
[0029] In the mixing device according to the invention, gas-gas
mixing is effected upon quenching and upon passage of gas through
the downcomers for gas 12 and/or swirl chamber 7.
[0030] The liquid leaving swirl chamber 7 accumulates on
pre-distribution tray 15, where it passes downwardly to
distribution tray 13 beneath through openings 17 or, sometimes, by
breaching the overflow weir 16. Gas is deflected by the
pre-distribution tray 15 and flows to the distribution tray 13.
[0031] At the distribution tray 13, equilibrated gas and liquid
phases are brought together. The distribution tray 13 serves two
purposes. Firstly, it evenly distributes liquid and gas before the
fluids enter a lower reaction bed 2b and, secondly, it allows
contact between liquid and gas to provide liquid-gas
interaction.
[0032] In FIG. 2, one of the downcomers for gas 12 of FIG. 1 is
shown in greater detail. The downcomer 12 has a gas inlet opening
19 located above collection tray 6, a radial gas outlet opening 20,
located below collection tray 6, a fluid deflector plate 21 located
above gas inlet opening 19, and a curved plate 22 to direct the gas
that passes through the downcomer to radial outlet opening 20.
* * * * *